Changing of node's checked state is slow in treeview

I have a Map control on a Form. The map control contains a collection of layers which each have a "IsVisible" to hide or show the layer.

I have a TreeView control with CheckBoxes with each node representing a layer, all contained under a single parent node.

When I check/uncheck a node, I want the related layer's IsVisible property to be set equal to the node's checked state.

Here's what I'm currently doing:

private void LayerTreeView_AfterCheck(object sender, TreeViewEventArgs e)
{
    if (e.Node.Parent == null) //if it's a parent node, make any children nodes match its checked state
    {
        foreach (TreeNode node in e.Node.Nodes)
        {
            node.Checked = e.Node.Checked;
            Map.BeginInvoke((MethodInvoker)delegate () { Map.FindFeatureLayer(node.Name).IsVisible = node.Checked; });
        }
    }
    else //it's a child node
    {
        Map.FindFeatureLayer(e.Node.Name).IsVisible = e.Node.Checked;
    }
    Map.BeginInvoke((MethodInvoker)delegate () { Map.Refresh(); }); //culprit is here
}

The problem is that there is a noticeable lag which increases with the more layers/nodes I have. In the code above, the last line contains the Map.Refresh();

The nodes don't update visibly until the Map.Refresh() is called, which is called for each node that has it's checked state changed. This causes the delay. I need the nodes to update immediately. It doesn't matter if the Map control lags behind with it's refresh, but it shouldn't be the opposite.